The present invention relates to a holding device usable for an automatic self-aligning ball metal of which the outer peripheral surface is spherical.
Generally, this kind of automatic self-aligning ball metal is held under the effect of resilient force by allowing a plurality of pawls formed on a metal holder (retaining plate) to come in pressure contact with the outer peripheral surface thereof. With respect to the conventional automatic self-aligning ball metal, it is known that slide torque required for the purpose of self-aligning of the ball metal increases correspondingly as resilient force of the pawls increases. Accordingly, it is preferable that the resilient force of the pawls be reduced in order to assure that automatic self-aligning is effected smoothly. However, when the resilient force of the pawls is reduced, they cannot satisfactorily oppose a load exerted on the ball metal in the radial direction or in the axial direction, resulting in a reliable supporting function being maintained only with much difficulty. Thus, it is preferable that the resilient force of the metal holder be kept at a lower level in order to have a reduced slide torque, while it is preferable that it be kept at a higher level in order to satisfactorily oppose a load exerted on the ball metal. Accordingly, the resilient force of the metal holder is required to have two contradictory characteristics. However, since the conventional metal holder is so constructed that each of the pawls has the same resilient force, it cannot have the aforesaid contradictory characteristics. In view of the fact as mentioned above, the existent state relative to the metal holder is such that reliable supporting of a shaft is taken into first consideration and a function of smooth self-aligning is sacrificed to some extent. Consequently, slide torque required for the ball metal is increased and thereby self-aligning cannot be achieved smoothly. Another drawback is that when the metal holder is so fitted that the pawls have a predetermined resilient force, it has a narrow range of adjustment and fitting is satisfactorily achieved only with much difficulty.